802.11 is a family of specifications for wireless local area networks (WLAN's) developed by a working group of the Institute of Electrical and Electronics Engineers (IEEE). There are currently four specifications in the family: 802.11, 802.11a, 802.11b, and 802.11g. All four use the Ethernet protocol and carrier sense multiple access with collision avoidance (CSMA/CA) for path sharing.
Within the 802.11 specifications, stations, for example mobile communication devices, can receive beacon frames from an access point to provide protocol and signal quality information. If, however, the beacon frame transmission rate is not sufficient, the stations can enter an active scan mode whereby the stations transmit probe requests to the access point. The probe requests signal the access point to transmit probe responses which provide protocol and signal quality information. Such an active scanning mechanism is described in §11.1.3 of the IEEE 802.11 specification.
There are disadvantages associated with a station operating in the active mode and sending probe requests. Notably, much overhead traffic is generated when multiple stations each generate probe requests and an access point transmits a probe response for each probe request. Further, the transmission of probe requests and additional channel sensing while contending for a channel is energy intensive. Consequently, the transmission of probe requests by a station decreases the station's battery life. Thus, what is needed is a solution such that a station can receive probe responses without the need for the station to continually transmit probe requests.